# Modern Physics

posted by
**Phil**
.

(7) Show that if a particle moves at an angle θ with respect to the x-axis with speed u in frame S, then it moves at an angle θ′ with the x′-axis in frame S′ with

tanθ′ = sinθ /( γ(cos θ − v/u))

Assume that S′ moves in the +x direction with velocity v with respect to frame S, and that the two x-axes are parallel.